Bio Mendelian Genetics

Gregor Mendel

• Austrian monk who observed garden pea plants to study inheritance

• AKA “Father of Genetics” bc of his discoveries

Inheritance

the passing of traits to the next generation

What does inheritance occur through?

gametes, which are sex cells (ie egg or sperm)

How is a diploid offspring formed?

You get one haploid gamete (egg) from mom and one haploid gamete (sperm) from dad

What do you inherit?

traits

Traits

a specific characteristic of an individual (ex. seed color). Determined by:

• genes

• environmental factors

• combination of both

True breeding

constantly produce offspring with only one form of a trait (ex. some pea plants only produce yellow seeds and some pea plants only produce green seeds)

Self-fertilize

the male gamete within a flower combines with the female gamete in the same flower (pea plants self-fertilize)

Cross pollination (in pea plants)

a male gamete from one flower of one one pea plant can fertilize a female gamete from a completely different pea plant

In order to truly understand the concept of inheritance, what did Mendel perform?

cross-pollination by transferring male gametes from the flower of a true breeding green-seed plant to the female organ of a flower from a true breeding yellow seed plant

What is the green-seed plant and yellow-seed plant generation called?

parent generation or P generation

What did the Parents (green-seed plant and yellow-seed plant) produce?

seeds of the next generation, known as the F1 generation (first filial generation)

What did the F1 generation produce?

all yellow seeds

What happened when Mendel then cross 2 plants from the F1 generation where he allowed them to self pollinate?

Mendel’s results for the F2 generation:

• 6022 yellow seeds

• 2001 green seeds

Ratio= 3 yellow seeds to 1 green seed

What did Mendel also discover from the F2 generation?

some were smooth and some were wrinkled

What did Mendel observe?

• seed color

• flower color

• seed shape/texture

• stem length

• flower position

What did Mendel’s discoveries lead him to form?

an idea about alleles

allele

alternative form of a single gene passed on from one generation to another generation

• Ex: seed color → one allele results in a green color and another allele results in a yellow color

What did the conclusion that the 3:1 ratio of the pea plant colors could be explained if the alleles were paired in each of the plants lead to?

the idea of dominant and recessive alleles

Dominant allele

the form of a trait in which only one version of that allele needs to be present for that specific trait to be expressed

• For Mendel, the dominant allele was the form of the trait that appeared in the F1 generation

• expressed with an uppercase letter

Recessive allele

the form of a trait in which both alleles need to be exactly the same for that specific trait to be expressed

• For Mendel, the recessive allele was the trait that was masked in the F1 generation

• expressed with a lowercase letter

What can alleles be in a diploid organism?

homozygous or heterozygous

Homozygous

an organism has 2 of the same alleles

• Ex: YY or yy

Heterozygous

an organism has 2 different alleles for a trait

• Ex: Yy

Genotype

an organism's allele pairs

Phenotype

organism's observable characteristic or outward expression of an allele

Law of Segregation

states that 2 alleles for each trait separate during meiosis

• one allele from mom and one allele from dad

Hybrid

organism with two different alleles, aka heterozygous organism

Purebred

organism with two of the same alleles, aka homozygous organism

Sometimes a particular culture or geographic region will be more likely to carry the recessive allele

People tend to interbreed and the allele becomes more common for that group, making the recessive phenotype more likely

Reason to keep the recessive allele in the population

Those that carry the s gives individuals extra protection from malaria